Sandwich structures commonly include a pair of thin and rigid facesheet materials separated by a lightweight reinforcing core. Sandwich structures are widely used as structural components in both advanced aerospace and automotive designs due to their high specific strength and stiffness. Conventionally, the lightweight reinforcing core includes a closed-cell material, such as balsa wood, honeycomb, or closed-cell foam. Additionally, a series of holes are commonly drilled or otherwise machined through the core and one or more of the sandwich facesheets such that the sandwich structure may be connected to surrounding structures or subsystems by a series of fasteners. However, drilling holes through sandwich core materials, either open or closed cell, may damage the core. Alternatively, conventional methods for embedding fasteners in a sandwich structure while maintaining the structural integrity of the core are time-consuming and costly.
Additionally, conventional core materials have a compression strength that is significantly less than the facesheets, which limits the amount of torque that can be applied to the fasteners connecting the sandwich structure to a surrounding structure or subsystem (i.e., over-torqueing the fasteners may disadvantageously collapse the core). Furthermore, conventional core materials (e.g., honeycomb or foam) cannot be threaded, and therefore the fasteners connecting the sandwich structure to a surrounding structure or subsystem can only transmit mechanical loads through the facesheets (i.e., because conventional core materials are designed to be lightweight, and thus have a low ratio of reinforcing material to air, the fasteners extending through the core are inefficient at transmitting mechanical loads because of the minimal contact area between the fasteners and the core). Moreover, machining fastener holes in the facesheets introduces a potential fluid leak path (i.e., the fastener holes break the continuity of the facesheets and allow for fluid to leak into or out of the core through the fastener holes). Accordingly, the fastener holes must be sealed to prevent fluid ingress into the core, which otherwise may degrade or corrode the core. Sealing of the fasteners is also a concern when a conventional sandwich structure is adapted to be used in a multi-function manner, such as for acoustic isolation, active heating or cooling, and/or fluid storage (e.g., a structural fuel tank).